<HTML>
<BODY BGCOLOR="white">
<PRE>
<FONT color="green">001</FONT>    /*<a name="line.1"></a>
<FONT color="green">002</FONT>     * Copyright (C) 2008-2012, fluid Operations AG<a name="line.2"></a>
<FONT color="green">003</FONT>     *<a name="line.3"></a>
<FONT color="green">004</FONT>     * FedX is free software: you can redistribute it and/or modify<a name="line.4"></a>
<FONT color="green">005</FONT>     * it under the terms of the GNU Affero General Public License as<a name="line.5"></a>
<FONT color="green">006</FONT>     * published by the Free Software Foundation, either version 3 of the<a name="line.6"></a>
<FONT color="green">007</FONT>     * License, or (at your option) any later version.<a name="line.7"></a>
<FONT color="green">008</FONT>     * <a name="line.8"></a>
<FONT color="green">009</FONT>     * This program is distributed in the hope that it will be useful,<a name="line.9"></a>
<FONT color="green">010</FONT>     * but WITHOUT ANY WARRANTY; without even the implied warranty of<a name="line.10"></a>
<FONT color="green">011</FONT>     * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the<a name="line.11"></a>
<FONT color="green">012</FONT>     * GNU Affero General Public License for more details.<a name="line.12"></a>
<FONT color="green">013</FONT>     * <a name="line.13"></a>
<FONT color="green">014</FONT>     * You should have received a copy of the GNU Affero General Public License<a name="line.14"></a>
<FONT color="green">015</FONT>     * along with this program.  If not, see &lt;http://www.gnu.org/licenses/&gt;.<a name="line.15"></a>
<FONT color="green">016</FONT>     */<a name="line.16"></a>
<FONT color="green">017</FONT>    <a name="line.17"></a>
<FONT color="green">018</FONT>    package com.fluidops.fedx.optimizer;<a name="line.18"></a>
<FONT color="green">019</FONT>    <a name="line.19"></a>
<FONT color="green">020</FONT>    import java.util.ArrayList;<a name="line.20"></a>
<FONT color="green">021</FONT>    import java.util.List;<a name="line.21"></a>
<FONT color="green">022</FONT>    <a name="line.22"></a>
<FONT color="green">023</FONT>    import org.openrdf.query.algebra.TupleExpr;<a name="line.23"></a>
<FONT color="green">024</FONT>    import org.openrdf.query.algebra.Union;<a name="line.24"></a>
<FONT color="green">025</FONT>    import org.openrdf.query.algebra.helpers.QueryModelVisitorBase;<a name="line.25"></a>
<FONT color="green">026</FONT>    <a name="line.26"></a>
<FONT color="green">027</FONT>    import com.fluidops.fedx.algebra.EmptyNUnion;<a name="line.27"></a>
<FONT color="green">028</FONT>    import com.fluidops.fedx.algebra.EmptyResult;<a name="line.28"></a>
<FONT color="green">029</FONT>    import com.fluidops.fedx.algebra.NUnion;<a name="line.29"></a>
<FONT color="green">030</FONT>    import com.fluidops.fedx.exception.OptimizationException;<a name="line.30"></a>
<FONT color="green">031</FONT>    import com.fluidops.fedx.structures.QueryInfo;<a name="line.31"></a>
<FONT color="green">032</FONT>    <a name="line.32"></a>
<FONT color="green">033</FONT>    <a name="line.33"></a>
<FONT color="green">034</FONT>    /**<a name="line.34"></a>
<FONT color="green">035</FONT>     * Optimizer to flatten the UNION operations.<a name="line.35"></a>
<FONT color="green">036</FONT>     * <a name="line.36"></a>
<FONT color="green">037</FONT>     * @author Andreas Schwarte<a name="line.37"></a>
<FONT color="green">038</FONT>     *<a name="line.38"></a>
<FONT color="green">039</FONT>     */<a name="line.39"></a>
<FONT color="green">040</FONT>    public class UnionOptimizer extends QueryModelVisitorBase&lt;OptimizationException&gt; implements FedXOptimizer{<a name="line.40"></a>
<FONT color="green">041</FONT>    <a name="line.41"></a>
<FONT color="green">042</FONT>            protected final QueryInfo queryInfo;<a name="line.42"></a>
<FONT color="green">043</FONT>                    <a name="line.43"></a>
<FONT color="green">044</FONT>            public UnionOptimizer(QueryInfo queryInfo) {<a name="line.44"></a>
<FONT color="green">045</FONT>                    super();<a name="line.45"></a>
<FONT color="green">046</FONT>                    this.queryInfo = queryInfo;<a name="line.46"></a>
<FONT color="green">047</FONT>            }<a name="line.47"></a>
<FONT color="green">048</FONT>    <a name="line.48"></a>
<FONT color="green">049</FONT>            @Override<a name="line.49"></a>
<FONT color="green">050</FONT>            public void optimize(TupleExpr tupleExpr) {<a name="line.50"></a>
<FONT color="green">051</FONT>                    tupleExpr.visit(this);<a name="line.51"></a>
<FONT color="green">052</FONT>            }<a name="line.52"></a>
<FONT color="green">053</FONT>            <a name="line.53"></a>
<FONT color="green">054</FONT>            <a name="line.54"></a>
<FONT color="green">055</FONT>            @Override<a name="line.55"></a>
<FONT color="green">056</FONT>            public void meet(Union union) {<a name="line.56"></a>
<FONT color="green">057</FONT>                    <a name="line.57"></a>
<FONT color="green">058</FONT>                    // retrieve the union arguments, also those of nested unions<a name="line.58"></a>
<FONT color="green">059</FONT>                    List&lt;TupleExpr&gt; args = new ArrayList&lt;TupleExpr&gt;();<a name="line.59"></a>
<FONT color="green">060</FONT>                    handleUnionArgs(union, args);<a name="line.60"></a>
<FONT color="green">061</FONT>                    <a name="line.61"></a>
<FONT color="green">062</FONT>                    // remove any tuple expressions that do not produce any result<a name="line.62"></a>
<FONT color="green">063</FONT>                    List&lt;TupleExpr&gt; filtered = new ArrayList&lt;TupleExpr&gt;(args.size());<a name="line.63"></a>
<FONT color="green">064</FONT>                    for (TupleExpr arg : args) {<a name="line.64"></a>
<FONT color="green">065</FONT>                            if (arg instanceof EmptyResult)<a name="line.65"></a>
<FONT color="green">066</FONT>                                    continue;<a name="line.66"></a>
<FONT color="green">067</FONT>                            filtered.add(arg);<a name="line.67"></a>
<FONT color="green">068</FONT>                    }<a name="line.68"></a>
<FONT color="green">069</FONT>                    <a name="line.69"></a>
<FONT color="green">070</FONT>                    // create a NUnion having the arguments in one layer<a name="line.70"></a>
<FONT color="green">071</FONT>                    // however, check if we only have zero or one argument first<a name="line.71"></a>
<FONT color="green">072</FONT>                    if (filtered.size()==0) {<a name="line.72"></a>
<FONT color="green">073</FONT>                            union.replaceWith(new EmptyNUnion(args, queryInfo));<a name="line.73"></a>
<FONT color="green">074</FONT>                    }<a name="line.74"></a>
<FONT color="green">075</FONT>                    <a name="line.75"></a>
<FONT color="green">076</FONT>                    else if (filtered.size()==1) {<a name="line.76"></a>
<FONT color="green">077</FONT>                            union.replaceWith(filtered.get(0));<a name="line.77"></a>
<FONT color="green">078</FONT>                    }<a name="line.78"></a>
<FONT color="green">079</FONT>                    <a name="line.79"></a>
<FONT color="green">080</FONT>                    else {<a name="line.80"></a>
<FONT color="green">081</FONT>                            union.replaceWith( new NUnion(filtered, queryInfo) );                   <a name="line.81"></a>
<FONT color="green">082</FONT>                    }<a name="line.82"></a>
<FONT color="green">083</FONT>            }<a name="line.83"></a>
<FONT color="green">084</FONT>            <a name="line.84"></a>
<FONT color="green">085</FONT>            /**<a name="line.85"></a>
<FONT color="green">086</FONT>             * Add the union arguments to the args list, includes a recursion <a name="line.86"></a>
<FONT color="green">087</FONT>             * step for nested unions.<a name="line.87"></a>
<FONT color="green">088</FONT>             * <a name="line.88"></a>
<FONT color="green">089</FONT>             * @param union<a name="line.89"></a>
<FONT color="green">090</FONT>             * @param args<a name="line.90"></a>
<FONT color="green">091</FONT>             */<a name="line.91"></a>
<FONT color="green">092</FONT>            protected void handleUnionArgs(Union union, List&lt;TupleExpr&gt; args) {<a name="line.92"></a>
<FONT color="green">093</FONT>                    <a name="line.93"></a>
<FONT color="green">094</FONT>                    if (union.getLeftArg() instanceof Union) {<a name="line.94"></a>
<FONT color="green">095</FONT>                            handleUnionArgs((Union)union.getLeftArg(), args);<a name="line.95"></a>
<FONT color="green">096</FONT>                    } else {<a name="line.96"></a>
<FONT color="green">097</FONT>                            args.add(union.getLeftArg());<a name="line.97"></a>
<FONT color="green">098</FONT>                    }<a name="line.98"></a>
<FONT color="green">099</FONT>                    <a name="line.99"></a>
<FONT color="green">100</FONT>                    if (union.getRightArg() instanceof Union) {<a name="line.100"></a>
<FONT color="green">101</FONT>                            handleUnionArgs((Union)union.getRightArg(), args);<a name="line.101"></a>
<FONT color="green">102</FONT>                    } else {<a name="line.102"></a>
<FONT color="green">103</FONT>                            args.add(union.getRightArg());<a name="line.103"></a>
<FONT color="green">104</FONT>                    }<a name="line.104"></a>
<FONT color="green">105</FONT>            }<a name="line.105"></a>
<FONT color="green">106</FONT>    <a name="line.106"></a>
<FONT color="green">107</FONT>    }<a name="line.107"></a>




























































</PRE>
</BODY>
</HTML>
